improve assertions message on function pointer errors

2 files changed, 7 insertions, 3 deletions

diff --git a/emscripten.py b/emscripten.py
index cb9eefab..eeb53bf7 100755
--- a/emscripten.py
+++ b/emscripten.py
@@ -1010,7 +1010,11 @@ def emscript_fast(infile, settings, outfile, libraries=[], compiler_engine=None,
             if other != sig:
               extra += other + ': " + debug_table_' + other + '[x] + "  '
           extra += '"); '
-        asm_setup += '\nfunction nullFunc_' + sig + '(x) { Module["printErr"]("Invalid function pointer' + pointer + 'called with signature \'' + sig + '\'. Perhaps this is an invalid value (e.g. caused by calling a virtual method on a NULL pointer)? Or calling a function with an different type, which will fail?"); ' + extra + ' abort(x) }\n'
+        asm_setup += '\nfunction nullFunc_' + sig + '(x) { Module["printErr"]("Invalid function pointer' + pointer + 'called with signature \'' + sig + '\'. ' + \
+                     'Perhaps this is an invalid value (e.g. caused by calling a virtual method on a NULL pointer)? ' + \
+                     'Or calling a function with an incorrect type, which will fail? ' + \
+                     '(it is worth building your source files with -Werror (warnings are errors), as warnings can indicate undefined behavior which can cause this) ' + \
+                     '"); ' + extra + ' abort(x) }\n'
 
     basic_vars = ['STACKTOP', 'STACK_MAX', 'tempDoublePtr', 'ABORT']
     basic_float_vars = ['NaN', 'Infinity']
diff --git a/tests/test_other.py b/tests/test_other.py
index 8b507306..678fa90d 100644
--- a/tests/test_other.py
+++ b/tests/test_other.py
@@ -556,10 +556,10 @@ f.close()
     else:
       # fastcomp. all asm, so it can't just work with wrong sigs. but, ASSERTIONS=2 gives much better info to debug
       test(['-O1'], 'abort') # no useful info
-      test(['-O1', '-s', 'ASSERTIONS=1'], '''Invalid function pointer called with signature 'v'. Perhaps this is an invalid value (e.g. caused by calling a virtual method on a NULL pointer)? Or calling a function with an different type, which will fail?
+      test(['-O1', '-s', 'ASSERTIONS=1'], '''Invalid function pointer called with signature 'v'. Perhaps this is an invalid value (e.g. caused by calling a virtual method on a NULL pointer)? Or calling a function with an incorrect type, which will fail? (it is worth building your source files with -Werror (warnings are errors), as warnings can indicate undefined behavior which can cause this)
 Build with ASSERTIONS=2 for more info.
 ''') # some useful text
-      test(['-O1', '-s', 'ASSERTIONS=2'], '''Invalid function pointer '1' called with signature 'v'. Perhaps this is an invalid value (e.g. caused by calling a virtual method on a NULL pointer)? Or calling a function with an different type, which will fail?
+      test(['-O1', '-s', 'ASSERTIONS=2'], '''Invalid function pointer '1' called with signature 'v'. Perhaps this is an invalid value (e.g. caused by calling a virtual method on a NULL pointer)? Or calling a function with an incorrect type, which will fail? (it is worth building your source files with -Werror (warnings are errors), as warnings can indicate undefined behavior which can cause this)
 This pointer might make sense in another type signature: i: _my_func  
 ''') # actually useful identity of the bad pointer, with comparisons to what it would be in other types/tables